Organic electronics is an emerging field of technology which aims to realize low-cost and environmentally-friendly fabrication of electronic devices. Organic field effect transistors (“FETs”) are potential alternatives to amorphous silicon transistors, and may be useful for instance in relatively low-speed devices with utility as pixel drivers of active matrix displays and in radio frequency identification devices. Potential advantages to making organic FETs instead of silicon- or other inorganic-based transistors include the possibilities of large-area and low-temperature processing, which may for example help enable fabrication of electronics on flexible plastic substrates.
Films of inorganic semiconductors are often brittle and inflexible, such that their fabrication into devices may be carried out on rigid silicon wafers yielding devices that themselves are inflexible. Films formed from organic semiconductors, in contrast, are often bendable and flexible, such that their fabrication into devices may potentially be carried out by a continuous process using, for example, a flexible web support body. The resulting devices themselves also have the potential to be bendable and flexible, opening up possible end use applications that are often impracticable for inorganic semiconductor-based devices.
Electronic devices having organic semiconductor films typically include a dielectric body that is adjacent and bonded to at least one face of the semiconductor film. Such a dielectric body may serve, for example, as a structural support for the semiconductor film, and as an electrical insulator for the semiconductor film to prevent shorting in the devices. In the case of an FET, the dielectric body also facilitates the high capacitance needed to induce charge carrier mobility in the source-drain channel. Desirably, such film and body elements are bonded together by the direct formation of one of such elements on the other. In order to carry out such formation, one of the elements is often deposited in vapor form on the other. For example, an organic semiconductor may be vaporized onto a pre-formed dielectric film web. However, carrying out such vaporization processes with sufficient precision to generate an organic semiconductor film of acceptable uniformity is difficult, particularly where the semiconductor film is continuously deposited onto a flexible web support in order to fabricate multiple active devices. In addition, vaporization often requires high temperatures which may cause degradation of the molecules of the organic semiconductor, and/or of the dielectric film contacted by the semiconductor vapor. Vaporization of precursors for making the dielectric film may similarly cause degradation of the molecules, oligomers or polymers used to form the dielectric film.
Accordingly, there is a need for new processes that permit the formation of a dielectric film in a liquid phase on an organic semiconductor, and new processes that permit the formation of an organic semiconductor film in a liquid phase on a dielectric film.